Clad metal



Jan. 27, 1953 Filed Jan. 30. 1948 L. J. LIEBERMAN 2,626,457

GLAD METAL 8 Sheets-Sheet l Jan. 27, 1953 L. J. LIEBERMAN CLAD METAL 8 Sheets-Sheet 2 Filed Jan. 30, 1948 INVENTOR Jan. 27, 1953 J. LIEBERMAN CLAD METAL Filed Jan. 50, 1948 8 Sheets-Sheet 3 J 56 F ,50 4/ 46 a 4/14 2 43 F 4 I {A q d K 1/, 60 'l) o) 60 F j 5/ J 0 INVENTOR 49 J5 4'6 44 ZWJZ m ATTORNEYS 27 3953 L. J. LIEBERMAN GLAD METAL 8 Sheets-Sheet 5 Filed Jan. 30. 1948 INVENTOR ATTORNEYS Jan 27, 11953 L. .11. LBEBERMAN GLAD METAL Filed Jail. 30, 1948 8 Sheets-Sheet 6 ll... J. LIEBERMAN Jan, 27, E953 CLAD METAL 8 Sheets-Sheet 7 Filed Jan. 30, 1948 INVENTOR ATTORNEYS Jan, 27 N53 L. J. LIEBERMAN CLAD'METAL 8 Sheets-Sheet 8 Filed Jan. 50, 1948 INVENTOR ATTORN EYS I Patented Jan. 27, 1953 UNITED STATESPATENT OFFICE CLAD METAL Leon J. Lieberman, Philadelphia, Pa.

Application January 30, 1948, Serial No. 5,427

8 Claims.

The present invention relates to the manufacture of clad metal, and to the composites employed and the clad metal produced.

The process subject matter of the present application is embodied in my copending application Serial No. 84,173, filed March 29, 1949, for Clad Metal. A further development of the process is covered by my copending application Serial No. 163,975, filed May 24, 1950 for Clad Metal. The blank is covered by my copending application Serial No. 163,976, filed May 24, 1950, for clad metal.

A purpose of the present invention is to simplify and facilitate the incorporation of nonhomogeneous ingredients such as abrasive in the surface layers of clad metals, or produce plates or sheets made up entirely of metal mixed with non-homogeneous ingredients such as abrasive.

A further purpose is to permit the rolling of layers of metal particles which initially exhibit little ductility without the development of serious cracks and breaks in the work under the rolls.

A further purpose is to accomplish the compacting, welding, bonding, reduction in thickness and sintering of powder metal layers by hot rolling, while protecting against breakage throughout the rolling operation.

A further purpose is to clean one side of each of two weldable or fusible metallic backings, applying a layer of weldable or fusible metal particles to the clean side of each backing, bring the backings together with the layers between them and separate from one another, join the backings around the edges to make composites, soak the composites at hot rolling temperatures, and hot roll the composites to eliminate porosity in the layers, weld the metal particles of each layer, bond each layer to its backing and reduce the thickness.

A further purpose is to interpose a confining and parting sheet between the layers and preferably to unite the sheet to the backing so that one backing and layer may be inverted and superimposed on another without having that layer drop away from the upper backing.

A further purpose is to make up the particle layers of a mixture of weldable or fusible metal particles with abrasive or refractory non-metallic particles.

A further purpose is to place a rim around each backing on the clean side, place the backings with the rims and clean sides uppermost, insert the layers of particles into the space defined by the rims against the clean sides of the backings, place a parting sheet over one layer and backing, unite the sheet at its edges to the rim, invert the back- 2 ing and layer provided with the parting sheet, superimpose it on the other backing above its layer and rim, and then unite together the rims around the outer edge.

A further purpose is optionally to compact the particles before the composites are completed and optionally to sinter the particles before they are placed in the composites and after compacting A further purpose is optionally to compact the particles by pressure applied to the layer against the backing and confined at the edges by the rim.

A further purpose is to make the backing and permissibly also the metallic particles of constructional iron alloy containing not over 0.55 per cent carbon.

A further purpose is optionally and preferably to employ the layers of particles in the composites in loose uncompacted form.

A further purpose is to employ backings and optionally to employ layers having stainless steel for the backings and the metallic particles of the layers.

A further purpose is to use particles which range between 6 and 100 mesh per linear inch for the abrasive and between 6 and 300 mesh per linear inch or finer for the metal particles.

A further purpose is to employ between 5 and per cent, preferably, between 20 and 30 per cent, of abrasive, in the abrasive layer.

A further purpose is to use an abrasive containing layer which comprises from 5 to 80% of the plate or steel thickness.

Further purposes appear in the specification and in the claims.

In the drawings I have chosen to illustrate a few only of the various embodiments in which my invention may appear, choosing the forms shown from the standpoints of convenience in illustration, satisfactory operation and clear demonstration of the principles involved.

Figure 1 is an enlarged diagrammatic section of the metal particles employed in the layers.

Figure 2 is an enlarged diagrammatic section of the abrasive particles which are used.

Figure 3 is an enlarged diagrammatic section of the mixture of metal particles and abrasive particles which is employed.

Figure 9 is a top plan view showing the backing and rim with the layer of particles applied inside the rim.

' alloy or composition in the clad layer, without the Figure 10 isa top plan view of a parting sheet.

Figure 11 is a side elevation of Figure 10.

Figure 12 is a diagrammatic side elevation showing two backings and layers, one of which has been provided'with a parting sheet and is superimposed above the other to combine in making a composite.

Figure 13 is:a side elevation of a completed composite.

Figure 14 is a diagrammatic sectional view of a soaking pit in which the composites have been placed.

Figure 15 is a diagrammatic side elevation of a composite undergoing hot rolling.

Figure 16 is a diagrammatic fragmentary plan view of a completed composite which is rolled down and is about to be trimmed around the edges as shown. I

Figure 17 is a diagrammatic partially sectional side elevation of a backing sheet and rim showing the application of a flux.

Figure 18 is a view corresponding to Figure 1'7 showing the application of a deoxidant.'

Figure 19 is a fragmentary diagrammatic central vertical section showing pressing of articles.

Figure 20 is a. diagrammatic central vertical sectional view of a sintering furnace.

Figure 21 is a top plan view of a modification showing the layer made up of compressed biscuits.

Figure 22 is a diagrammatic partially sectional side elevation of a variation showing pressing of the layer applied directly to the backing.

Figure 23 is a fragmentary side elevation, partly in section, of a variation in the composite.

Figure 24 is an enlarged diagrammatic transverse section of the complete composite showing the mounting of a single abrasive particle.

Figure 25 is a top plan view of the completed composite showing the abrasive surface.

Figure 26 is an enlarged transverse sectional view showing the bond line of the clad metal.

In the drawings like numerals refer to like parts throughout.

In the prior art efforts have been made to produce floor plate and the like in which non-homogeneous particles such as abrasive (including refractory) are distributed or embedded in metal, by casting molten metal around the abrasive particles and employing the product in the form as cast. Difliculty has been encountered because of the tendency of the abrasive or the like to segregate due to difierence in specific gravity and because of the limited utility possessed by the structure when used in the as cast form.

Efforts have also been made in the prior art to apply a layer of metallic particles, for example a bearing layer, on a backing strip, and to apply rolling pressure directly to the layer and strip. The ability to reduce the thickness of the section has been limited to compacting of the particles, as theapplication of substantial rolling pressures as employed in hot rolling has not been possible without breakage of the layer of particles due to the limited ductility.

By the present invention it has been possible to obtain clad metals which can undergo normal reductions in hot and in some cases cold rolling and permit the production of sheet and plate having rolled clad layers containing non-homogeneous ingredients such as abrasive, and having the properties in the baekings normally secured in similar hot and cold rolled metals. It is likewise possible by the invention to obtain any convenient difiiculty which is otherwise encountered in roll- 'ing clad materials of dissimilar characters.

The layer which is incorporated by cladding will suitably mainly comprise powdered metal which is capable of welding to itself and to the backing layer. For many purposes the composition of the layer to be applied on the backing will be a constructional iron alloy containing not ,over 0.55 per cent carbon, such as iron of practically carbonless grade, low carbon steel (for example 0.01 to 0.20 per cent carbon), medium car- 'bon steel (0.20 per cent carbon to 0.55 per cent carbon), low alloy weldable steel (5'per cent total of hardenability alloying ingredients including any one or more of nickel, chromium, manganese, molybdenum, vanadium, silico'n, and the like) and containing carbon up to 0.35 per cent nominal. All of these materials will have the usual metalloids and residual or intentional alloy ingredients which are commonly employed in constructional iron and steel.

If desired the powdered metal may comprise stainless steel, whether of the chrome-nickel grade (for example 18 per cent chrominum, 8 per cent nickel nominal) or of the straight chromium grade (for example 16 per cent chromium).

Likewise the powdered metal may be of the copper base alloy type, such as copper, brass, bronze, beryllium copper, or the like. Also the powdered metal may be of the nickel alloy type (such as nickel, Monel, K Monel, inconel, or the like). Where the base metal is of suitable character to weld or fuse therewith the metal products may also be of aluminum, aluminum base alloy, magnesium or magnesium base alloy.

In any case where the metals chosen will weld or fuse, adequately with one another and with the base, mixtures of two or more of such metal ticles lose their identity. Good results can be obtained with mesh sizes ranging between 6 and 300 mesh per linear inch or finer, particles finer than mesh per linear inch being employed if the expense is justified. For satisfactory commercial results mesh sizes between 30 and 100 mesh per linear inch are usually quite adequate.

Figure 1 shows metal particles 40 of the character that will be employed.

. The abrasive, where abrasive isused, will preferably be a refractory abrasive which will retain the form of discreet unmolten particles during hot rolling. For this purpose non-metallic refractory particles such as alumina, silica, magnesia, chrome iron ore, zirconium dioxide and silicon carbide are very satisfactory. I

The sizes of the abrasive particles for good results should range between 6 "and 100 mesh per linear inch, preferably between 10 and 60 mesh per linear inch.

While certain aspects of the invention are useful without employing abrasive particles, for the manufacture of floor plates and the like it is best to employ between 5 and 50 per cent of abrasive particles based upon the total of metal plus abrasive particles. For ordinary commercial purposes the most satisfactory range is between 20 and 30 per cent. Unless otherwise stated, all percentages given herein are by weight.

Figure 2 shows abrasive particles 4| of the character which will be employed. No attempt is being made to show the actual contours of the particles.-

The abrasive particles will conveniently be mixed with the metal particles to achieve a homogeneous mixture 42 as shown in Figure 3."

, of hot rolling of the particular backing. Any one of the metals already referred to in reference to the metal products may be used for the backing metal provided the metal of the backing will adequately weld with the metal of the metal particle layer. For most commercial purposes .the backing will be employed as a structural member, and therefore constructional iron alloy containing not in excess of 0.55 per cent of carbon will be best in most cases. While carbonless iron can be used, the advantage of increased physical properties will normally lead to the use of low or medium carbon constructional steel or low alloy weldable steel of the compositions already explained in connection with the powdered metal. For special applications stainless steel as already described may be employed, as well as the copper group of alloys (copper, brass, bronze, beryllium copper and the like) or the nickel group of alloys (nickel, Monel, K-Monel, inconel and the like). Where the powdered layer will adequately weld therewith the backing metal may also be aluminum or aluminum alloyv or magnesium or magnesium alloy.

The backing 44 as shown in Figues and 6 is conveniently rectangular in major dimensions and often will have a thickness in the range between 1 and 12 inches, preferably about 2 inches. A convenient size for each of the other dimensions is to 96 inches or greater. 7

In some cases a flux may be desirable, although ordinarily it has been found by the present inventor that a flux is not necessary. The flux or bonding layer if used will vary with the nature of the metal powder and the backing metal as well known, and no attempt will be made to review all of the known fluxes or bonding layers which might be employed. With nickel and chromium alloys generally, comprising either the metal pow-' der er the backing, when the other member is iron or steel, nickel flake has proved to be very satisfactory as flux. Nickel flake is suitable with the various grades of stainless steel. When copper base alloy forms one or both of the members to be bonded, any good bronzing flux is suitable.

Where iron or steel is to be bonded to iron or steel, particularly where one of the alloys contains substantial amounts of chromium or nickel, an electrodeposited or sprayed layer of iron or nickel may to advantage be used, in accordance with Houston, U. S. Patents 2,225,868 and 2,147,407, and Armstrong, U. S. Patents 2,044,742 and 1,997,538.

It has been found that in most cases the use of a deoxidant is not necessary, especially as the metal powder has a large surface and comparatively large amounts of oxygen can be present without serious consequence. This is a distinct advantage of the present procedure over the prior practice of bonding a sheet to a backing layer. Where a deoxidant is us aluminum or magnesium powder, metallic calcium or sodium or a hydride such as calcium hydride may be employed to advantage.

6 In accordance with the present invention the powder layer is applied to the backing layer by making-. up composites. Th mating face of the backing'layer should be thoroughly cleaned and for this purpose the surface 45 to be welded or fused is preferably shot blasted- Other cleaning techniques may be used whether by mechanical abrasion for example through grit or sand blasting, or chemical removal as by pickling or electrochemical removal as-by electrolytic etching.

' Whatevercleaning step is employed. the resulting surface should be clean and dry.

On the clean surface around the edge of the backing a rim 46 is applied, conveniently by welding or fusing. If substantial delay or soilage is to be involved in the technique of applying the rim, the cleaning of the surface at 45 should be accomplished after applying the rim, but if the application of the rim is carefully controlled, the cleaning can be accomplished prior to the application of the rim. The rim is best made by applying side members 41 and end members 48 conveniently of rectangular (preferably approximately square) cross section, suitably of the same composition as the backing and welded or fused to the backingat 49 all around the periphery and at 50 where the various ends meet. The welding may be continuous or discontinuous and no serious harm is done by slight gaps or porosity in the weld as long as there is secure anchorage between the rim and the backing. Optional vent holes 5| may be provided extending through the rim to permit escape of interior gases.

The backings after being provided with the rims are filled with the layers of particles against the clean sides. This is best accomplished by placing each backing with the clean side and rim uppermost and depositing the desired particle composition 52 in the space defined by the rim on top of the clean surface 45. While as later explained these particles may be previously compacted and even previously sintered in the preferred embodiment, the particles applied at 52 will be entirely loose and uncompacted as indicated at Figure 9 and will preferably fill the space up to substantially the top of the rim.

The backings with the layers of particles will be employed in sets, each set preferably consisting of a pair. and particle layer will conveniently be left resting upright as shown at 53 in Figure 12 while the other backing of the pair will conveniently be inverted after being closed by a parting sheet. The parting sheet 54 as shown in Figures 10 and 11 may conveniently be a metal sheet of the same material as the backing, coated on its opposite sides or faces at '55 and 56 with a partin material which extends nearly to the edges but preferably is omitted in a band 51 around the edges on each side, to aid in welding. The parting material may conveniently be a refractory such as magnesia, alumina, chrome iron ore, ferric oxide, or the like, made into a paint with a vehicle such as shellac, linseed oil or turpentine and One of the backings with its rim The separator side (top and bottom) with clean surfaces directed inwardly and toward one another, a layer of particles against each clean surface and within a confining rim and a parting sheet between the respective layers which are otherwise adjoining. The rims are then joined around their edges, preferably by a weld 80 which bridges over the space occupied by the parting sheet and joins the backings by Joining the rims.

The composites are then soaked at hot rolling temperature following the usual procedure for soaking preliminary to hot rolling of the metals involved.

In Figure 14 a conventional soaking pit BI is shown containing composites 62 which are placed on end after the manner of soaking ingots and billets. The soaking has a definite effect in partially sintering the particles together, beginning th process of uniting the particles to one another and to the backing which is carried forward and completed during the hot rolling. Where iron and steel are involved, the soaking time will preferably be from 2 to 4 hours at temperatures of 1800 to 2400" F., preferably 2000 to 2400 F., and most desirably 2250 to 2400 F. Of course, the soaking temperature must not be high enough to melt any component, and if any metallic component melts at the lower limit of the hot rolling temperature of another metallic component, the present process will not be applied to such components in such combination.

Experience has indicated that no special soaking precautions are required other than those indicated for the metals employed.

The composites are rolled, following the usual rolling procedure for the metal of the backing. For iron and steel, blooming and heavy duty plate mills are most suitable. The hot rolling performs a number of different functions. In the first place it accomplishes a function similar to pressing, eliminating porosity and compacting the particles without the necessity and the expense and delay incident to pressing on a conventional powder metallurgy press. At the same time, as porosity is eliminated and the particles form a dense mass, the particles weld to one another and bond to the backing. Thus the action involves the effects of pressing and sintering, and also marked plastic flow which gives much more compacting than would be possible under ordinary pressing and sintering.

As in ordinary rolling practice, the work is widened and elongated, reducing to any suitable gage, for example plate thickness such as 1 $4; or inch, or sheet thickness such as 10 gage or lighter. area of 18 by 20 inches was increased to 40 by 100 inches during the rolling and an initial thickness of 1% inches was reduced to inch. The abrasive containing layer will often be 5 to 80% of 'the final thickness, usually 20 to 50%. The hot work can be followed by cold work so far as the ductility will permit. During the first pass or first few passes, air in the interior space between the particles of the layers and in other voids escapes through the vent holes 5! already described, but the vent holes are then pinched closed or substantially closed and no tendency is noted to draw in air during any later point in the rolling process.

The particles of abrasive go through the roll-v ing without any tendency to segregate and are firmly held in the compacted particle layer which finally results.

In Figure 15 rolling mill rolls 63 are illustrated which are reducing the section at N to indicate one, of numerous passes which may be used.

Cross rolling may be employed if desired. When the product is rolled to gaze. the edges are trimmed as by a shear to eliminate the edge strip 85 which will be imperfect due to the rolling down ofthe rim and the weld beads. The individual sheets are then stripped apart, the separator discarded and the final product consists of a backing 68 and a face cladding layer 61 thoroughly united and welded at a bond line it (Figure 26) and having discrete particles of abrasive it throughout the layer l1 and uniformly distributed over the surface as shown in Figure 25. Actually the metal tends to form a layer over the abrasive as shown in enlargement at 10 (Figure 24) Experiments indicate that the bond to the backing is excellent. and the product will undergo fianging, bending and other normal forming without separation of the bond or breakage of the clad face. Unlike the cast products of the prior art, the face layer can wear clear through to the bond line without encountering any difference in distribution of the abrasive or other added particles. Of course, it will be evident that where desired the particle layer may be made up of several particle layers with different Thus in a particular example, an initial compositions, in which case the percentage of abrasive or other nonmetallic ingredients may vary if desired from top to bottom.

The invention is applicable wherever clad metals are to be made, since it overcomes the difficulty in rolling dissimilar metals and permits the adding of a facing layer having disadvantageous hot rolling characteristics at the temperature required for hot rolling of the backing. Thus for such purposes the composition as shown at 52 in Figure 9 may be entirely metal particles without abrasive or other added material.

In most cases the invention will, however, find its best application in making fioor plates, and products of this character are widely used in stairway treads and landings, floors, vestibule floors, railroad car steps, fire escape fioors and steps, kitchen floors, machine and industrial walkways, and running boards for box cars.

The following may be cited as examples.

Example I Example II Example II is the same as Example I except that the powdered abrasive is magnesia.

Example III Example III is the same as Example I except that the powdered metal is stainless steel of composition 18 per cent chromium and 8 per cent nickel, nominally no carbon.

Example IV Example IV is the same as Example I except that the abrasive makes up 30 per cent of the particle layer.

Example V Example V is the same as Example I except that the backing is low alloy weldable steel of Example VI Example VI is the same as Example I, except that the particle layer is 100 per cent plain carbon steel of AISI 1020 grade.

Example VII Example V11 is the same as Example I except that the particle layer is 100 per cent of stainless'steel, nominally 18 per cent chromium, .8 per cent nickel, no carbon.

Example VIII Example VIII is the same as Example Lexcept that the metal particles consist of brass containing '70 per cent of copper and 30 per cent of zinc.

Example IX Example IX is the same as Example I except that the metal particles consist of bronze containing 90 per cent of copper and 10 per cent of tin.

Example X Example X is the same as Example I except that the metal particles consist of Monel.

Example XI Example XI is the same as Example I except that the particle layer consists 100 per cent of inconel.

Example XII Example XII is the same as Example I except that the backing and metal particles consist of 24 S aluminum alloy.

While for many purposes it is preferred to apply-the particles as loose uncompacted powder which'is compacted by the rolling, to omit flux and omit deoxidant, and avoid sintering prior to soaking, these features may optionally be used in individual cases.

Figure 17 illustrates the use of flux 1|, in this case nickel flake, applied to the clean surface of the backing before introducing the layer 52 of metal particles usually with abrasive.

Likewise there is shown in Figure 18 the application of a deoxidant layer 12 preferably on top of the particle layer 52. The deoxidant layer in this case may be aluminum powder where the particle layer consists of steel powder with abrasive.

While as already explained the rolling will ordinarily perform the pressing function and avoid the expense of pressing, the particles may be formed at 13 (Figure 19) into a biscuit or briquette prior to introducing them into contact with the clean surface of the backing. Where preforming is employed, the surface of the particle layer Which is to come into contact with the clean surface of the backing should be cleaned as by shot blasting prior to contact. Anyconventional press 14 may be employed in preforming.

The preforming pressure will preferably be of the order of 1000 to 10,000 pounds per square inch. The preformed particles may also be sintered prior to making the composite if desired. A sintering furnace I is illustrated, heated electrically at 16 for sintering particle layers 11 permissibly in an inert or preferably reducing atmosphere at 18 applied through connections [9. Suitable gases are hydrogen,

carbon monoxide. nitrogen, ammonia, helium or argon or mixtures thereof. The surface of the sintered layer which is to come into contact with the clean surface of the backing should be cleaned as by shot blasting before the composite is assembled.

sintering may be accomplished with or without pressing. For the present purpose a loose mass of particles may be slntered.

For iron or steel the sintering temperature may range between 1200 and 1800 F. permissibly up to 2400 F. and preferably at about 1550 F.

preferably for a time of one and one-half to' three hours. Where an inert or reducing atmosphere is used, the layers should cool in the atmosphere.

In case pressing is to be employed, it is very expensive to use large presses, and individual biscuits or' priquettes 80 as shown in Figure 21 may be assembled inside the rim of the backing to form the particle layer. It has been found that these weld perfectly along their lateral edges during rolling. provided such edges are cleaned before making up the composite.

Where pressing is to be employed, the backing and rim may form part of the mold as shown in Figure 22. In this case the press 8| has a die 82 which just fits within the limits of the rim and brings pressure against the backing held in a suitable cooperating die 83. The pressing may take place in steps, adding more particles as the layer iscompacted.

While for many purposes the most convenient form of the. invention will employ two backings and two particle layers in the composite, it will be understood that any plurality of backings and layers may be used preferably in multiples of two. Figure 23 illustrates a composite made up of four backings 84, 85, 86 and 81 each with a particle layer adjoining. Where the two backings 85 and 86 would otherwise be juxtaposed, an additional parting sheet 88 is applied and the edges of the backings are welded at 89.

It will be evident that by the present invention it is possible cheaply and conveniently to fabricate clad metal sheets containing nonhomogeneous material such as abrasive, and to roll out, compact, weld and bond metals which otherwise are difiicult to roll and impossible to reduce to thin layers as required for clad metals.

While the invention has its widest application in the making of floor plates it will be understood that the principles of the invention can be used in many of the connections where it otherwise would be diilicult to unite together the particular combination of metals which is employed.

When reference is made to the particles or layers as being welded, it will be understood that they may be fused.

In view of my invention and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention without copying the process and product shown, and I, therefore, claim all such insofar as they fall within the reasonable spirit and scope of my claims.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A composite comprising a pair of spaced weldable metallic backing blocks each having a clean interior face directed toward the other, a layer of loose uncompacted particles adjoining the clean face of each backingand comprising a l1 mixture of weldable metal particles and refractory non-metallic particles. a parting sheet interposed between the layers in contact therewith, a rim around the edges. and weld metal joining together the backing blocks and rim around the edges.

2. A composite comprising a pair of spaced weldable metallic backing blocks having irmer clean surfaces directed toward one another, a layer of particles comprising a mixture of weldable metallic particles and abrasive nonmetallic particles adJoining the clean surface of each backing block, a parting sheet between and in contact with the layers having weld-resisting properties, a rim around the composite between the backing blocks and welds joining the rim to the backing blocks.

3. A composite according to claim 2, in which the metallic backing blocks are of constructional iron alloy containingnot in excess of 0.55 per cent carbon.

4. A composite according to claim 2, in which the metallic particles comprise nickelbase alloy.

5. A composite according to claim 2, in which the backing blocks and metallic particles are of copper base alloy.

6. A composite according to claim 2, in which the backing blocks and metallic particles are of aluminum base alloy.

7. A composite according to claim 2, in which the backing blocks and metallic particles are of magnesium base alloy.

8. A composite comprising a pair of spaced weldable metallic backing blocks, a parting sheet between and in spaced elation to each of the blocks having weld-resisting properties, a layer 12 of particles on each side of and in contact with the parting sheet extending from the parting sheet to one of the metallic backing blocks, comprising a mixture of weldable metallic particles and abrasive non-metallic particles, the layer of particles at each side of the parting sheet being compacted, welded together and welded to one of the backing blocks, and means including welds Joining together the backing blocks at the edges.

. LEON J. LIEBERMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 717,080 Coleman Dec. 30, 1902 1,469,761 Yunck Oct. 2, 1923 1,886,615 Johnson Nov. 8, 1932 1,904,568 Taylor Apr. 18, 1933 2,094,538 Ingersoll Sept. 28, 1937 2,160,559 Orr May 30, 1939 2,169,354 Chace Aug. 15, 1939 2,178,527 Wellman "Oct. 31, 1939 2,190,310 Chace Feb. 13, 1940 2,225,868 Huston Dec. 24, 1940 2,365,083 Jarrett Dec. 12, 1944 2,381,941 Wellman Aug. 14, 1945 2,390,452 Mudge Dec. 4, 1945 2,416,400 Mehl Feb. 25, 1947 2,438,759 Liebowitz- Mar. 30, 1948 FOREIGN PATENTS Number Country Date 568,786 Great Britain Apr. 20, 1945 

